# deduction guides for `std::function_ref`

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< cpp‎ | utility‎ | functional‎ | function ref

Defined in header `<functional>` |  |
template< class F > function_ref( F* ) -> function_ref<F>; | (1) | (since C++26)
template< auto f > function_ref( std::nontype_t<f> ) -> function_ref</*see below*/>; | (2) | (since C++26)
template< auto f, class T > function_ref( std::nontype_t<f>, T&& ) -> function_ref</*see below*/>; | (3) | (since C++26)

1) This overload participates in overload resolution only if std::is_function_v<F> is true.
2) Let type F be std::remove_pointer_t<decltype(f)>. This overload participates in overload resolution only if std::is_function_v<F> is true. The deduced type is std::function_ref<F>.
3) Let type F be decltype(f). This overload participates in overload resolution only if :

- F is of the form R(G::*)(A...) noexcept(E) (optionally cv-qualified, optionally noexcept, optionally lvalue reference qualified) for a type G, or
- F is of the form M G::* for a type G and an object type M, in which case let R be std::invoke_result_t<F, T&>, A... be an empty pack, and E be false, or
- F is of the form R(*)(G, A...) noexcept(E) for a type G.

    The deduced type is std::function_ref<R(A...) noexcept(E)>.

### Example

| This section is incomplete Reason: no example

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